In accordance with a rapid spread of information relevant apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry. A lithium battery has been presently noticed from the viewpoint of a high energy density among various kinds of batteries.
Liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. On the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery.
In the field of such an all solid state battery, the intention of improving the performance of all the solid state battery has been conventionally attempted while noticing an interface between an active material and a solid electrolyte material. For example, in Patent Literature 1, an electrode body containing an active material whose surface is coated by 70% or more with a first solid electrolyte such as lithium niobate and a second solid electrolyte such as a sulfide is disclosed. This intends to decrease interface resistance between the active material and the second solid electrolyte such as a sulfide by coating the surface of the active material with the first solid electrolyte such as lithium niobate.
On the other hand, in Patent Literature 2, a polymer battery such that the surface of an electrode active material for the polymer battery is compactly coated with a coating layer containing a lithium conductive inorganic solid electrolyte and conductive fiber is disclosed.